The present invention relates to a compact pump provided with an exhaust valve device and a hemodynamometer employing the compact pump. Specifically, the invention relates to a compact pump which supplies air to an air chamber such as a cuff of the hemodynamometer to raise the pressure in the air chamber, and then releases the air to lower the pressure in the air chamber.
Such a compact pump is incorporated in, for example, an oscillometric hemodynamometer. In the oscillometric hemodynamometer, a pump supplies air to a cuff wound around an upper arm of a patient to compress an artery at a predetermined pressure to temporarily block a blood stream, and the air is then released by a normal exhaust valve to gradually lower the pressure in the cuff. Incidentally, the variations of the internal pressure of the cuff and the vibration amplitude in accordance with the artery pulsations are processed by a microcomputer to measure the systolic blood pressure and the diastolic blood pressure. After the measurement processing, a rapid exhaust valve is operated to rapidly lower the internal pressure of the cuff.
Generally, it is preferable that the normal exhaust valve which is employed in the hemodynamometer has such a property that the pressure in the cuff is lowered at a constant speed of about 3 to 4 mmHg/sec., and the rapid exhaust valve has such a property that the pressure in the cuff is rapidly lowered.
FIG. 5 shows such a compact pump which is disclosed in Japanese Patent Publication No. 2002-106471A.
A compact pump 1 comprises: a pump body 2 which is driven by a motor (not shown); a normal exhaust valve 3 which exhausts an air through a slit at a constant speed (such an exhaust valve is disclosed in Japanese Utility Model Publication No. 63-14809Y, for example); a rapid exhaust valve 4 which is actuated by a plunger; and a flexible tube 5.
The normal exhaust valve 3 and the rapid exhaust valve 4 are separately provided from the pump body 2. The tube 5 interconnects an exhaust port 6 of the pump body 2, the normal exhaust valve 3 and the rapid exhaust valve 4, and is also connected to a cuff (not shown) which is wound around an upper arm of a patient. Inside the tube 5, there is formed an air passage 8 which communicates respectively with a pump chamber 7 in the pump body 2, the normal exhaust valve 3, the rapid exhaust valve 4, and the cuff.
With the above configuration, when the pump body 2 is driven, exterior air is introduced into the pump chamber 7 and is then supplied to the cuff from the exhaust port 6 via the air passage 8 formed in the tube 5. When the internal pressure of the cuff reaches a predetermined pressure, the normal exhaust valve 3 is activated to exhaust air in the air passage 8. Incidentally, a larger amount of air than the amount of the air exhausted by the normal exhaust valve 3 is introduced into the cuff from the pump chamber 7.
Here, since the driving of the pump body 2 is halted, the internal pressure of the cuff is gradually lowered by the normal exhaust valve 3. Incidentally, the variations of the internal pressure of the cuff and the vibration amplitude in accordance with the artery pulsations are processed by a microcomputer to measure the systolic blood pressure and the diastolic blood pressure. After the measurement processing, a rapid exhaust valve 4 is activated to rapidly lower the internal pressure of the cuff.
In the above configuration, since the normal exhaust valve 3 and the rapid exhaust valve 4 are separately provided from the pump body 2, a large number of the components are required, the structure becomes complicated, thereby increasing the manufacturing cost.
Moreover, a piping structure of the tube 5 (the air passage 8) becomes complicated. Since the tube 5 is exposed to the exterior of the pump body 2, the tube 5 might sometimes come into contact with other members and bent or crooked when the compact pump 1 is assembled, thereby lowering the workability of the assembling operation.
Further, a plunger for exclusive use is adopted as an actuator for the rapid exhaust valve 4, thereby increasing the component cost.